The cxx-conversion
+branch has been merged into trunk. This switches GCC's implementation
+language from C to C++.
+Additionally, some data structures have been re-implemented in C++
+(more details in the merge
+announcement). This work was contributed by Lawrence Crowl and
+Diego Novillo of Google.

Caveats

+

GCC now uses C++ as its implementation language. This means that
+to build GCC from sources, you will need a C++ compiler that
+understands C++ 2003. For more details on the rationale and specific
+changes, please refer to the C++ conversion
+page.

To enable the Graphite framework for loop optimizations you now
need CLooG version 0.17.0 and ISL version 0.10. Both can be obtained